In programming, code reuse is often performed by a developer including an instruction in parent code that makes a call to target code, such as a library or a method in another class. In such a situation, the target code has a single defined input control point, which executing the instructions in the target code starts. Similarly, the position to which execution returns in the parent code is a single well-defined position. Code reuse may alternatively involve a developer copying the instructions of the target code directly into the parent code.